ToEE came out just last year. All I know if you have the option to get married to a gay man.

They're all very different. NWN is ok, but you only play one person and you have a (mostly) autonomous sidekick if you want them.
IWD2 Pretty much like the first one, or BG series as far as play is concerned.
ToEE does indeed cap at 10th which was annoying 'cos there's enough XP for about 12th(at a guess), it is by far the hardest of the three, and the copy I had, even post patch was buggy as hell(some quests made impossible by non-recognition of completion etc). Having said that it was quite enjoyable, it's turn based as opposed to real time, it's 3.5 not 3rd ed.
800X600 should be ok, but best to check the requirements on the box/site.
Multiclassing is available, but was a bit limited if I remember, certainly in NWN to only 3 classes.

I played the first NWN when it was release. You get one person and a choice of (limited to one) different companions. Some are about useless, but do have their uses.

IWD2 I played from beginning to end, I think i finished the game (normal mode, there is HoW mode after first ending) at around 16th level.

Of course you can multi-class, with some limitations. Pretty decent game, if you enjoyed the first one or the BG series.

As for ToEE, it is Return to ToEE. Turn based, as previous poster stated. For me it was sluggish game play, with a lot of limitations, such as party alignment limitation (which i did not like at all). Was a very constricting game (to me, even in the beginning).

Pretty sure NWN and IWD2 are default 800x600 resolution, most programs run that default resolution now.

AFAIK there are no prestige classes available in the *Original* NWN and IWD2, but i am NOT sure about ToEE.

Hope that helps a little.

NWN, & its expnasions are worth it. With hordes of the udnerdark u get assloads of rpestige classes and epic level.

NWN is ultimately customisable. It doesn't have something you want? You can make it have something you want. Take a look at the City of Doors Initiative, a group making a full set of custom tilesets, races, and possibly even classes meant to replicate the Planescape campaign setting for NWN.

TOEE does cap at 10. Excess XP beyond that is only good for item creation by your spellcasters. The party alignment thing is a pain as it limits what alignments you can give your PCs. The only other thing it seems to majorly affect is your opening quest, AKA "Why you came to Hommlet to begin with". NPCs don't seem to care much what alignment you are. There are no prestige classes but I think you can otherwise multiclass to your heart's content. It does have some bugs but there are patches that clear most if not all of them up. Love interests are in the game if you choose to pursue them. There's two female NPCs that will join the party if one of your male PCs marries them. There's a male NPC who can be romanced by a female PC and even married as part of the epilogue if you take it that far. I think there is a gay male NPC who can be wooed if you're into that. (never tried) There's also a brothel in Nulb (unlocked by 3rd party patch) where you can even engage in a little girl-girl action as part of a quest. The ending is pretty open-ended as you can choose multiple paths. The epilogue is entirely dependent on what actions you choose throughout the adventure. You are free to kill everything in the temple and defeat evil or you can join the temple and act to further evil. Or even somewhere in between. I enjoyed it. You do need a good system to run it well though.

The great Matt has spoken!